The NFL’s chief medical officer says it is “really important” for the league and the NFL Players Association to determine whether marijuana can be used as an effective and safe pain-management tool for players.

“I think we have a lot more to learn about that,” Allen Sills, a Vanderbilt University neurosurgeon hired by the NFL in March, said in a phone interview Wednesday. “Certainly the research about marijuana and really more particularly cannabinoid compounds as they may relate to the treatment of both acute and chronic pain, that is an area of research that we need a lot more information on and we need to further develop.

“I think that’s part of what we hope to accomplish together working together with the Players Association,” Sills said. “I think this is really important because I like to talk about that our approach to caring for players is really holistic. We want to talk about health and safety issues that affect the whole player experience. And certainly pain management is a big part of that.”

The league sent a letter to the NFL Players Association in July offering to work together on research into the potential use of marijuana for pain management for players. The NFLPA has been conducting its own study on the issue and so far has not responded to requests for comment on the NFL’s offer.

The letter is the clearest indication yet that the league might be willing to work cooperatively with the union on the issue. Marijuana use is banned under the sport’s collectively bargained drug policy and players face disciplinary measures, including suspensions, for positive tests.

“These really aren’t just football issues,” Sills said. “These are society issues, right? We know right now that as a society that the treatment of both acute and chronic pain is a huge public health problem. In fact, I think I just saw some recommendations of a congressional panel coming out asking that the president declare a national state of emergency about opioid use in this country. So these are societal issues. But I think that we in professional sports are in a unique position to help inform the public and to do research and really advance our state of understanding about this issue.”

Sills addressed a variety of topics in a nearly half-hour interview Wednesday. He said it is “very clear that there are long-term health risks associated with repetitive head injuries” and acknowledged the significance of a study by researchers from Boston University and the VA Boston Healthcare System which found evidence of the degenerative brain disease CTE in 110 of 111 brains of former NFL players studied.

“I think this is another important contribution from the Boston University group,” Sills said. “They’ve obviously been a leader in this space and helping to define and describe the pathology of CTE. And I think it’s another important piece of this puzzle that we’re trying to put together. I think that I like to describe CTE ally is a puzzle where we’re trying to assimilate pieces to better understand it, because there’s so much we don’t understand with regard to causation and incidence and who’s exactly at risk, and what are the risk factors and what things might we modify and certainly treatment. So we have a lot left to learn. But this is obviously another key piece as we move forward.”

NFL leaders sent mixed public signals last year about their view as to whether a link between football and CTE has been definitively established. After league executive Jeff Miller suggested to a congressional committee that such a link does exist, Dallas Cowboys owner Jerry Jones said it was “absurd” to contend that such a link had been established beyond all doubt because “medicine is evolving.”

Asked about that, Sills said: “I think it’s very clear that there are long-term health risks associated with repetitive head injuries, particularly if they’re not treated properly. That’s something that’s been established since 1928. A pathologist named Harrison Martland first described a syndrome in boxers where he talked about the effects of repetitive head blows. So I think that association is very well known. But I agree, again, with a lot of medical experts that we still have a lot of unanswered questions about cause, about incidence, prevalence and long-term effects such as CTE, particularly why some people that play football and other contact-collision sports develop this condition and the vast majority do not.”

Sills said the league updated its concussion protocols for the upcoming season based on the latest accepted worldwide medical standards and practices. Beginning with Thursday night’s Hall of Fame Game in Canton, Ohio, between the Dallas Cowboys and Arizona Cardinals, all sideline concussion evaluations of players will be conducted in medical tents, which are being utilized by the NFL for the first time.

Sills brought together all the medical personnel involved in the league’s game-day concussion evaluations for an offseason training session. He spoke to the referees, who are involved in identifying players with concussion symptoms. He has been working with Thom Mayer, the NFLPA’s medical director.

He said he will continue to practice at Vanderbilt, treating athletes’ nerve and spine injuries. He spends a great deal of time, he said, at the league offices in New York, where he works in the office formerly occupied by former Super Bowl-winning coach Tom Coughlin, who left to take a front office job with the Jacksonville Jaguars. Sills said he travels regularly to visit individual NFL teams and attend medical and research meetings. He hopes to continue, to the extent that it’s possible, working Friday nights at high school games and Saturdays at college games, in addition to coaching youth sports.

“The very first time I ever met with the commissioner,” Sills said of Roger Goodell, “the first words out of his mouth were, ‘Player health and safety is our number one priority. And if you take this job, we want you to help make sure that we get that right. We want to be leaders and we want to be setting the tone for sports medicine care throughout the world.’

“And I obviously was reassured to hear that, not only from him but I also heard the same message from team owners and from other executives in the league and club personnel. That was obviously an important part of my decision-making to even consider taking the job. But it’s been gratifying to see that… . Everyone has really acted in accordance with that.”